The present invention relates to a navigation terminal mounted on a mobile unit, and more particularly to a navigation system including a terminal.
A car navigation system that is mounted on a vehicle that is a typical mobile unit displays a map on display unit, based on a current location of the vehicle positioned, with a mark indicating the current location of the self vehicle superposed on its map.
In the car navigation system, a positioning unit for positioning the current location of the vehicle includes a GPS (Global Positioning System) receiver and various self-contained navigation sensors for calculating the current location from the travel distance and the moving direction of the vehicle. Also, the map information for displaying a map on the display unit, the relevant information associated with the map information and various kinds of functional services are provided from an information center located outside the vehicle, employing a communication unit mounted on the vehicle.
There is a functional service as above described such that the information indicating the place of destination and the information indicating the current location as the place of departure are transmitted via a communication unit from a terminal mounted on the vehicle to the information center, and the information center searches a drive route on the basis of the received information, whereby the drive route information indicating the searched drive route is transmitted again via the communication unit from the information center to the terminal. In such a route searching functional service, when the terminal mounted on the vehicle receives the drive route information, it does not always follow that the total drive route information indicating the drive route connecting the place of departure and the place of destination is received at a time.
As an example in which the total drive route information is not received, the communication line connecting the terminal and the information center may be disconnected at the time of receiving data while the mobile unit is driven. Also, as another example, the information amount of total drive route information may exceed the storage capacity of the storage unit provided for the terminal.
In this manner, when the total drive route information is not received, the drive guide is not given, making it impossible to support the driving fully.